Wireless communication systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include code-division multiple access (CDMA) systems, time-division multiple access (TDMA) systems, frequency-division multiple access (FDMA) systems, and orthogonal frequency-division multiple access (OFDMA) systems.
By way of example, a wireless multiple-access communication system may include a number of base stations, each simultaneously supporting communication for multiple communication devices, otherwise known as user equipments (UEs). A base station may communicate with UEs on downlink channels (e.g., for transmissions from a base station to a UE) and uplink channels (e.g., for transmissions from a UE to a base station).
Communication systems may support communication over a carrier using multiple transmission layers. In some cases, the transmission layers may overlap in time and/or frequency. Such communication systems may take advantage of multiple antenna techniques for increased reliability or capacity. Multiple antenna techniques include transmit diversity, multiple-input multiple-output (MIMO) techniques and non-orthogonal multiple access (NOMA) techniques. Multiple antenna systems that employ T transmit antennas and R receive antennas may realize a capacity increase of min{T, R} over single antenna techniques. However, in a multiple access system, the possible variations in techniques employing multiple antennas including, for example, single-user MIMO (SU-MIMO), multiple-user MIMO (MU-MIMO), and NOMA results in challenges in optimizing channel scheduling over the space of possible transmissions to multiple UEs.